1. Field of the Invention
The present invention relates to a fish culturing system. More specifically, the present invention relates to a fish culturing system employing a culture tank with opposing water flows and a separate water purification unit that recycles water back to the culture tank via air lift tubes. The entire system is powered only by compressed air.
2. Description of Related Art
As more and more people are consuming fish to achieve health benefits, demand for commercially raised fish has increased. To meet this demand, a fish culturing system that is inexpensive and efficient to use is needed. Additionally, it is beneficial to have such a system indoors, rather than exposed to the elements.
To meet this increased demand and minimize space needed for the operation, the number of fish grown in a certain volume of water must be maximized. In increasing the number of fish per certain volume, several concerns must be addressed. Increased fish population means increased demand for oxygen from the same volume of water. Aeration of the water helps increase levels of dissolved oxygen for use by fish, thereby allowing an increase in the fish population. Of course increased population means increased feeding and increased waste production. Excess food and waste in the water begin to break down producing ammonia, which is toxic to fish even at low levels of concentration. Frequent water changes help alleviate this problem, but are costly and wasteful of the natural resource. Reuse and recycling of the water is therefore not only desirable, but environmentally and economically mandated. Water in the tank contains toxic levels of ammonia and suspended solids from fish wastes and food residues. Thus filters have been developed that remove suspended solids from the water by physical means, and convert deadly ammonia to harmless nitrate by biological filtration, before returning water back to the tank.
These filtering systems generally pump water from a rearing tank through an area having increased surface area harboring bacteria which convert the deadly ammonia to harmless nitrate, while a filter bed traps suspended solids before returning the water to the tank.
U.S. Pat. No. 3,888,210 which issued to Buss on Jun. 10, 1975, discloses a fish husbandry system utilizing at least partial recirculation of water. The system uses an inner and outer hood to deliver fresh water and recirculated water to the fish tank, after having passed through a filter. The water flows, by gravity, from the rearing tank to the filter, where it is reconditioned, before it is pumped back to the rearing tank via a water pump.
U.S. Pat. No. 4,806,237 issued to Ewald, Jr. on Feb. 21, 1989, discloses a waste removal apparatus. The device includes a tank through which water from a fish culture system may be circulated. Filters mounted in upright and spaced relation cross the tank so that the water circulates successively through them. Tubes are provided for injecting air into the water on the upstream side of each filter.
U.S. Pat. No. 4,427,548 which issued to Quick, Jr. on Jan. 24, 1984, discloses a filtering method and apparatus. The apparatus operates by pumping water from a process tank and passing it in a trickle filter fashion through an open-cell polymeric foam material.
U.S. Pat. No. 4,951,606 which issued to Hartung on Aug. 28, 1990, discloses a fish tank for intensive fish fattening and process for operating such a fish tank. The tank includes a pit into which a filter with vertically extending flow channels is placed. Water, along with air is circulated through these flow channels where the water is purified (nitrified) biologically according to the adhesive activated-sludge process.
U.S. Pat. No. 4,043,299 which issued to Birbeck, et al. one Aug. 23, 1977, discloses a fish rearing system. The system recycles water through a primary biological filter after which the water is aerated and returned to the rearing tank.
U.S. Pat. No. 4,892,651 which issued to Hill on Jan. 9, 1990, discloses a filtering system for fish ponds. The filter system includes chambers for harboring micro-organisms which clean organic waste from the water flowing through from the pond. A by-pass is included so that individual chambers may be taken out of line for cleaning. An air supply is also provided for supplying air to the micro-organisms.
U.S. Pat. No. 4,414,919 which issued to Hess on Nov. 15, 1983, discloses a flowdown rearing pond. The rearing pond includes a water recycling and filtering system, using a buoyant filter bed.
U.S. Pat. No. 4,211,183 which issued to Hoult on Jul. 8, 1980, discloses an apparatus including a fish tank having a biological filter submerged within the tank.
U.S. patent No. which issued to Engelbart on Oct. 27, 1992, discloses a device for raising aquatic animals. An apparatus with aerating devices arranged in pools or ponds producing a bubble curtain without creating turbulence in the water.
Although efforts have been made in the past to alleviate the concerns involved in raising fish in large numbers, the need still exists for a culture system that draws waste from surface and submerged locations, recycles and recirculates water, while aerating and nitrifying the water, efficiently and economically, without the additional costs of a water pump and its use.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.